The present invention relates generally to control tuning in a manufacturing process. Specifically, the invention relates to the optimization of one or more process control devices by measuring and collecting data on the physical properties of articles moving through a manufacturing process. More specifically, the present invention relates to the optimization of one or more process control devices used in cigarette manufacturing, through remote and/or in-line testing of individual cigarettes, and by collection of the test data in a central data base.
During cigarette manufacturing, it is necessary to measure and control the physical properties of the cigarettes being made. Differences between a target measurement for a given physical property of a cigarette and its actual measurement can lead to excessive scrap, wasted machine time or lost orders, as the end product may be rejected by a demanding customer. Several known devices have been designed and utilized to analyze the physical properties of cigarettes. These devices may monitor such properties as length, diameter, weight, texture, moisture content, hardness, and so forth. These known systems have generally failed to provide for adequate control over cigarette properties during manufacturing, however, due at least in part to the fact that such analyses typically occur off-line, and the results of the analyses are not available in real-time for use in adjusting the manufacturing process.
Use of these known devices typically requires that one or more cigarettes be periodically removed from a cigarette production line for testing. The cigarettes may be removed manually, or by automated machinery. The removed cigarettes are then generally supplied to a plurality of testing equipment in order to determine the aforementioned characteristics of an average cigarette. Once testing is completed, an operator can use the data to adjust the manufacturing process accordingly. For example, the operator might increase or decrease the amount of tobacco placed into the cigarette.
In U.S. patent application Ser. No. 09/966,317, which is hereby incorporated by reference herein, a system and method is disclosed for automatically tuning the weight control of a flow of materialxe2x80x94such as the flow of tobacco into a cigarette. The system and method described therein examines long term standard deviation that occurs during the manufacturing process and makes adjustments accordingly. More specifically, the system and method allows for the xe2x80x9cfine tuningxe2x80x9d of the manufacturing process, such that a given article, such as a cigarette, can be more accurately produced.
According to the system and method of U.S. patent application Ser. No. 09/966,317, weight measurements of a flow are captured at synchronized intervals over the length of the flow, and proportional and integral calculations are thereafter performed on these weight measurements. A weight measurement device is preferably used to capture the desired unit weight measurements of the flow at proper intervals over the length thereof. A control actuator, in communication with a controller and control loop, is preferably used to change the unit volume of the flow so as to sufficiently maintain a target unit weight. Based on the results of the proportional and integral calculations, the flow may be adjusted to compensate for the duration of any deviation in the weight measurements from a target weight, and further deviations may be anticipated such that the total amount of deviation is reduced.
The system and method of U.S. patent application Ser. No. 09/966,317 preferably employs a proportional, integral, derivative (PID) algorithm and control loop to make the calculations and adjustments necessary to fine tune the device. In certain embodiments of the present invention, preferably only the proportional and integral portions of the PID algorithm are utilized, although the derivative portion may also be used if desired.
Essentially, the proportional portion of the control loop measures the error or deviation between a setpoint weight value and a measured weight value of the flow. Under proportional control, an attempt is made to adjust the output of a flow adjusting device connected to the control actuator so that any error between the setpoint weight value and a measured weight value of the flow is removed. This is accomplished by the amount of change that will occur in the output of the control actuator as a result of a change to a corresponding input thereof. With error and gain known, the bias of the PID controller may then be adjusted (or the controller xe2x80x9cresetxe2x80x9d) in order to move the output of the control actuator as necessary to cause the weight of the flow to reach the setpoint value. The integral portion of the PID control loop is then used to continually and more accurately adjust the bias of the controller. Without the integral portion of the control loop, bias adjustments to the controller would have to be accomplished manually. To more accurately tune the device, the integral portion of the PID control loop may effect an automatic bias adjustment (automatic reset) whenever an error between the setpoint value and measured value are detected.
To accomplish fine tuning, small adjustments (bumps) are periodically and manually made to the input of the control actuator. In response to the input change, the output of the control actuator will cause movement of the flow adjusting device for a specified amount of time. Individual weight measurements are taken, preferably from a time before each bump to the input is initiated, through a time after the output has fully responded to the change in the input. Weight measurements are collected for each of the bumps, and the collected data is fed into an optimization program. Based on the collected data it receives, the optimization software can then generate tuned control parameters for use by the PID control loop. Therefore, by utilizing the tuned control parameters, the system and method of U.S. patent application Ser. No. 09/966,317 allows the mean weight of the material flow to be more quickly and more accurately adjusted and controlled than is possible with known systems and methods.
As described above, weight measurements of the flow are captured in real-time by locating a weight sensor in the path of the cigarettes as they are manufactured. Measurement data is stored in a database. The stored data is then properly compiled, and loaded into a control optimization program. Based on the collected data it receives, the control optimization software generates tuned control parameters which may then be input into the weight control system of the invention. The tuned control parameters allow the PID controller and control loop to more quickly and accurately adjust and control the mean weight of the material flow and subsequently produced cigarettes or other articles than would otherwise be possible. This process can also be employed to control other cigarette properties during manufacturing. By collecting appropriate data, an optimization program may be used to output control parameters for various control systems within the cigarette manufacturing process.
However, it is realized that certain measurements and data collection may often not be accomplished without first removing a cigarette, or cigarettes, from the production line for testing. It is still desirous, however, that the results of any off-line testing conducted on the removed cigarettes be available, preferably in real-time, for use in optimization of the ongoing manufacturing process. The collected data may also be analyzed during non-production periods, so that adjustments can be made once production resumes. The optimization process for a given control system may be substantially as described above with regard to weight control tuning, but may, of course, also be altered to best accomplish optimization of a particular manufacturing parameter. For example, it should be realized that control systems for adjusting cigarette properties such as length or diameter may be of significantly different design than the weight control system described above. Thus, it should be understood that the collected data relative to a particular cigarette property or characteristic can be operated on in various ways to produce the desired optimization parameters, and such parameters may be generated mindful of the design of the particular control device to which they will be provided.
To this end, it is contemplated that a central control system comprising a database and optimization software as disclosed in U.S. patent application Ser. No. 09/966,317 be centrally located and adapted for communication with a variety of remotely located testing equipment. The central control system can then be utilized to perform control tuning on the various individual control systems that regulate the cigarette properties. Each piece of testing equipment preferably provides test data to the central database, where the test data can be appropriately stored. Once a sufficient amount of data has been collected and stored regarding a specific cigarette property, the data may be fed to optimization software. The control parameters resulting from the optimization operation may then be fed to an appropriate control system to automatically adjust the manufacturing process, thereby controlling the cigarette property of interest.
The central control system may be connected to a multitude of different sensors and testing equipment, and to sensors and testing equipment from different manufacturers. Thus, the central control system of the present invention can be integrated into the cigarette manufacturing process even if the testing equipment used therein is from a plurality of different manufacturers. In this manner, it is also possible to accomplish automatic, rather than manual adjustment of manufacturing parameters, even though testing is done off-line. This is accomplished by placing each piece of testing equipment in communication with the database and optimization software of the central control system. Rather than depending on an operator to collect and analyze test data from a plurality of different equipment, at a variety of locations, all test data may be automatically sent to the central database as soon as testing is completed. Alternatively, the data collected by each piece of testing equipment may be supplied to the central database during a period of non-production, for use when production resumes. When the latter method is employed, the optimization software may act on the data, but adjustment of individual control systems may be reserved until production is again underway.
It should be understood that when using the central control system and method of the present invention with off-line testing equipment, cigarettes may be removed from the production line manually, or by automated equipmentxe2x80x94such as by robotic means. When automatic cigarette removal is utilized, a single removal device may remove the required number of cigarettes from the production line and distribute them amongst the existing testing equipment. Alternatively, more than one removal device may be employed for this purpose. Various equipment currently exists for accomplishing automatic removal and testing of cigarettes, and the central control system of the present invention is designed to interface with such equipment. The central control system of the present invention may also be adapted to control and direct this and other automatic cigarette removal equipment, such that test data can be obtained at desired intervals. The central control system of the present invention may also, in addition to communicating with various, existing equipment, control its operation. It is also possible to utilize a combination of in-line and off-line testing equipment to obtain the required data. In any case, the central database receives and stores measurement data from the various sensors and test equipment. The stored data may then be compiled or otherwise acted upon prior to its output to the optimization software. The optimization software then determines optimized control systems for input to the various control devices that regulate the cigarette manufacturing process.